1. Field of the Invention
The present invention relates to a lithographic apparatus and a device manufacturing method.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays, and other devices involving fine structures. In a conventional lithographic apparatus, a patterning means, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device), and this pattern can be imaged onto a target portion (e.g., comprising part of one or several dies) on a substrate (e.g., a silicon wafer or glass plate) that has a layer of radiation-sensitive material (e.g., resist). Instead of a mask, the patterning means may comprise an array of individually controllable elements that generate the circuit pattern.
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and scanners, in which each target portion is irradiated by scanning the pattern through the beam in a given direction (the “scanning” direction), while synchronously scanning the substrate parallel or anti-parallel to this direction.
There is a desire to be able to efficiently manufacture devices having relatively large and relatively low resolution areas of one type and associated relatively small and relatively high resolution areas of a different type. For example, in flat panel display (FPD) screens a first relatively large area comprises a large number of pixels intended to define an image to be displayed occupies all but the periphery of a rectangular area. The resolution within the pixel area is relatively low. However, electronic circuits are also provided to drive the individual pixels. These electronic circuits are arranged around the periphery of the pixel area. Generally, an elongate array of electronic circuits is provided along one horizontal side and one vertical side of the pixel area, although electronic circuits may be provided along all four sides of the pixel area.
The traditional approach to the manufacture of FPD screens has been to (1) produce the pixel areas using lithographic methods; (2) glue separately manufactured integrated circuits to the reverse side of the screen, and (3) connect the integrated circuits to the individual pixels of the pixel area. Design rules (e.g., critical dimensions etc) for integrated circuits are increasingly more stringent, and much more stringent that design rules for the pixel area of FPD screens. The pixel areas of FPD screen are continuously being improved, which, in combination with the rapid rate of design change for integrated circuits, means that the combination of components making up an FPD screen changes in design even more rapidly than either integrated circuits of the pixel areas of the screens. This presents real challenges to the manufacturers of FPD screens.